The present invention relates to that class of vehicles commonly referred to as xe2x80x9cwalking machines,xe2x80x9d which are large, non-wheeled power-driven structures operable for transporting massive and heavy loads, upwards of several thousand tons, over a surface, such as the ground, snow, a prepared gravel area, etc. These machines, massive and heavy substructures in themselves, are fabricated from iron and steel, and find particular utility in carrying and sequentially transporting huge structures such as oil drilling rigs to position them over pre-drilled conductor pipes installed into the ground prior to drilling well bores in a new field undergoing exploration for oil, or over existing well bores in old fields previously worked, as the case may be.
In particular, the method and apparatus of the present invention are directed to a novel system for sequentially transporting and steering a drilling rig and an accompanying service module, while substantially maintaining their relative positions, over an area in which multiple conductor pipes have been pre-drilled. The drilling rig and service module are each selectively transported and steered, if necessary, so that the drilling rig""s derrick is precisely aligned over a selected conductor pipe. Steering is accomplished by operators of the substructures which carry the drilling rig and service module coordinating the relative movements of their machines.
There are numerous examples of so-called walking machines which have been designed for use in moving drilling rigs over well bores which have been drilled in an area of oil exploration. An example of a known walking machine is disclosed in U.S. Pat. No. 5,921,336 issued to Reed in which a drilling rig substructure is provided with a plurality of lifting jacks, and each lifting jack is connected to a jack pad. Roller assemblies are mounted at the lower end of the lifting jacks and each jack pad has a center beam that the roller assemblies engage. The jack pads are rotatable in 360xc2x0 about a vertical axis. A push-pull mechanism extends between each jack pad and each roller assembly to move the rollers horizontally in relation to the jack pad. In operation, when it is desired to move to a well bore, the lifting jacks are extended, forcing the jack pad against the ground. Continued extension causes the upper end of the lifting cylinder to raise the substructure and accompanying drilling rig to move from ground level. The lifting jacks now remain in the extended position and the push-pull mechanisms are then actuated to move the substructure in a given direction. The lifting jacks are then retracted so that the substructure returns to the ground and the jack pad is then raised and moved to a new position.
The present invention is directed to a method and apparatus or substructure for transporting heavy machinery or equipment from one location to another, and more particularly to an apparatus which can be moved along a straight line or also steered. The apparatus can be steered so that it is displaced to align or orient equipment such as a drilling rig, precisely above a well bore.
It is conventional for an oil company or driller, drilling for oil, to install a row of xe2x80x9cconductorxe2x80x9d pipes, approximately ten feet apart, each conductor pipe extending down to a shallow depth usually 100 to 200 feet. When a drilling rig is positioned over a conductor pipe, and drilling commences, the drill will bore into the ground 8,000 feet or more to drill for oil. After the well is completed, the drilling rig is moved to the next conductor pipe, approximately ten feet away, and drilling commences again. While care has been taken initially to align the series of conductor pipes along a common line, they nonetheless can be offset from the line, sometimes as much as six inches. It is then necessary to adjust the location of the drilling rig to precisely align it over sequential conductor pipes.
The present invention provides a method and apparatus in which a substructure, supporting a drilling rig on a surface, may be lifted, shifted, and displaced from one conductor pipe to another, and, if necessary, steered into precise position over a conductor pipe. The present invention provides a steering mechanism, and also provides a construction in which a pair of substructures, one serving as a platform for the drilling rig and the other for a service module, can be moved, and steered, so that their relative positions are maintained. The service module, supported on a substructure separate from that of the drilling rig, provides the necessary auxiliary equipment for the drilling rig. This equipment includes engines, pumps, motors, pipe storage, fuel, and mud pumps, to name a few, necessary for operating the drilling rig. The service module is interconnected with the necessary hoses, pipes, electrical conduits, etc. to the drilling rig. The service module and drilling rig each have an operator""s cab, so that the operators of these two massive modules can control the necessary positioning of their respective substructures and loads. The drilling rig and service modules can together weigh upwards of 4-5,000 tons.
Because the method and apparatus for transporting the drilling rig and service module include similar substructures, lifting assemblies, and steering mechanisms, a summary of just the method and apparatus for transporting and steering the drilling rig will be set forth. A substructure for carrying the drilling rig includes a pair of spaced-apart frame structures, or main beams which support the drilling rig above the ground or surface. Extending through a central region of each of the main beams is an elongate track member or sub beam which is positioned on the surface, and upon which a main beam, when lifted, will be rolled along. Each sub beam is provided with a planar upper face, and a plurality of lift assemblies are mounted on the main beams directly above their respective sub beams. Each lift assembly includes a hydraulic cylinder rigidly mounted on the substructure and connected to a hydraulic pressure unit and controls operable for extending and retracting its associated ram. Mounted on the end of each ram is a roller assembly which includes a roller frame carrying a plurality of rollers, rotatable around a horizontal axis. Each of the roller assemblies is mounted for selective rotation about a vertical axis, and a steering arm, connected to a steering mechanism mounted on the main beam, is operable to selectively rotate the roller assembly and its roller frame about the vertical axis so that the rollers may be oriented to a preselected angle relative to the longitudinal axis of a sub beam. Connected to each sub beam is a shifter mechanism which is also connected to a main beam and is operable to shift the main and sub beams relative to one another.
Initially, it will be assumed that the drilling rig is to be translated or moved rectilinearly, i.e., on a straight line of travel. The main beams of the substructures are positioned on the ground, and the lifting assemblies have been actuated so that their rams are retracted, disengaging the roller assemblies and their rollers from the sub beams. The shifter mechanisms, which include a travel cylinder connected between the main beam and the sub beam, are actuated to extend its rod so that the sub beam is pushed rectilinearly in the direction of travel. The lifting cylinders are then actuated to extend their associated rams so that the rollers engage the upper face of the sub beams. The rams are further extended so that the main beams and their load are raised above the surface and supported on the rollers and the sub beams. The travel cylinders are then retracted to displace the main beams in the direction of travel, with the main beams being rolled along the upper face of their respective sub beams, and supported thereon. The lift cylinders are then actuated to retract their respective ram to lower the main beams to the ground, and then to disengage the rollers from the sub beam. This basic method can be repeated, to move the drilling rig in repeated cycles a distance equal to the stroke of the travel cylinder, or less, if that is required. An operator can position a drilling rig over a selected conductor pipe relatively precisely, assuming that the conductor pipes are laid out on a straight line, and that the drilling rig does not have to be steered. However, in many situations the rig does in fact require steering.
It is common that conductor pipes have not been precisely laid out on a common line, but are offset, and the method and apparatus of the present invention provides a steering mechanism enabling an operator to steer accurately the drilling rig into position over a selected conductor pipe. The operational sequence is generally as follows. With the travel cylinders fully extended, the main beams supported on the ground and the lifting cylinders fully retracted, the operator determines how much the main beams need to be steered to travel to the correct position over a conductor pipe.
The steering arms are positioned to set the roller assemblies and their frames at a predetermined angle relative to the longitudinal axis of the sub beams, and the lifting cylinders are then actuated so that the rams are extended to engage the sub beams such that the rollers make an angle relative to the sub beams"" longitudinal axes. The lifting cylinders are further extended to raise the main beams off the surface and the shifter mechanism is then actuated, moving the main beam on the rollers at an angle relative to their associated sub beams. There are multiple lifting cylinders which are interconnected by a linkage system, so that the roller frames can be preset at different angles relative to the longitudinal axis of a sub beam. Depending how the operator selects orientation of the rollers relative to the longitudinal axis, the main beams may be displaced straight ahead, with no steering, or the operator may choose to direct the main beams in so-called simple steering, crab steering, or complementary steering modes. These will be further described below with reference to the preferred embodiments of the invention.